1. Field of the Invention
This invention relates to a method for manufacturing an electronic device using a closed-type transport container.
2. Background Art
In the process for manufacturing a semiconductor device, basic compounds containing nitrogen atoms such as ammonia (NH3) and amines including primary to tertiary amines present in the manufacturing environment are known to cause dimensional variation by reaction with chemically-amplified resist. Hence the apparatus for the photolithography process using chemically-amplified resist is strictly controlled so as not to be contaminated with NH3 and amines present in the manufacturing environment. For example, a method is proposed for storing semiconductor substrates without varying the sensitivity of chemically-amplified resist applied thereto by controlling the ammonia concentration in the storage environment to a prescribed concentration (see, e.g., JP 11-125914A (1999)).
On the other hand, NH3 may occur not only from the manufacturing environment, but also from semiconductor substrates. For example, semiconductor substrates may be processed by dry etching using NH3 as an etching gas or chemical vapor deposition (CVD) of silicon nitride film. In these cases, NH3 adsorbed on the semiconductor substrate is introduced into the apparatus for the subsequent processes. Furthermore, polysilazane (PSZ) film formed by application of silazane perhydride contains unstable silicon-nitrogen (Si—N) bonds in the film, which are hydrolyzed during storage to release NH3. If such substrates producing NH3 are stored in a highly hermetic storage container like the Front Opening Unified Pod (FOUP), NH3 is accumulated in the container. For this reason, before lithography or other processes requiring NH3 contamination control, the container needs to be replaced by a container not contaminated, with NH3 for preventing contamination. However, container replacement unfortunately results in decreasing the production efficiency and increasing the manufacturing cost, such as increasing the number of processes, increasing the number of storage containers needed, and increasing the space for storing containers.